Coaxial Cable

Like a twisted pair, the coaxial cable consists of two conductors. However, its structure permits a wider range of frequencies. The coaxial cable consists of a hollow outer cylindrical conductor (solid or braided) which surrounds a single conductor (solid or stranded). The outer and inner conductors are separated by insulating strings or a solid dielectric material.

Categories

Coaxial cables are categorized by their radio government ratings (RG). Each RG number denotes a unique set of physical specifications, including the wire gauge of the inner conductor, the thickness and type of the inner insulator, the construction of the shield, and the size and type of the outer casing. Each category is adapted to a particular use.

Category	Impedance	Use
RG-59	75 W	Cable TV
RG-58	50 W	Thin Ethernet
RG-11	50 W	Thick Ethernet

Each type of coaxial cable has a characteristic impedance depending on its dimensions and materials used, which is the ratio of the voltage to the current in the cable. In order to prevent reflections at the destination end of the cable from causing standing waves, any equipment the cable is attached to must present an impedance equal to the characteristic impedance (called 'matching'). Thus the equipment "appears" electrically similar to a continuation of the cable, preventing reflections.

Connectors

The BNC (Bayonet Neill-Concelman) connector is used to connect the cable to a device. The BNC T connector is used to branch out another coaxial cable. The BNC terminator is used at the end of the cable to prevent reflection of the signal.

Advantages

1. Superior bandwidth and data rate compare to twisted pair (350Mhz – 500Mbps)
2. Shielded against crosstalk and external noise without the need for twists

Disadvantages

1. Susceptible to thermal noise and intermodulation noise
2. Rigid and heavy Cable
3. Higher attenuation compared to twisted pairs.